A potentially critical problem that may occur in high temperature and pressure power plant components is a leak type failure in the threaded closure portion of a welded on compression fitting. Such failures may be caused by galled or corroded threads, sheared off threads, extensive pit-type corrosion between the ferrule and fitting body, or cross-threading of the closure nut onto the body threads. Each failure of this type requires a replacement type repair of the fitting.
The problem of repairing a fitting of this type is intensified when the fitting is part of a precision type nozzle penetration for instrumentation when said such fitting is welded to a large immobile component such as a steam generator and which is located in a relatively inaccesible position. One of the major difficulties to be overcome with this type of problem is maintaining precise bore alignment between the existing nozzle run and the new replacement fitting without the aid of precision machine shop equipment.
In the piping field, various devices have been disclosed for working the end of a pipe. For example, in U.S. Pat. No. 2,744,269, (Kerr et al), a pipe threading die head assembly is disclosed. This assembly includes a pipe-grasping arbor which carries a sleeve of rubber or other suitable material which expands to grasp the interior surface of a pipe as a plug is drawn into the sleeve. Other pipe threading devices are disclosed in U.S. Pat. No. 1,231,743 (Johnston) and U.S. Pat. No. 2,757,393 (Galloway). The former patent includes an expandable member for tightly gripping the inside diameter of a pipe during cutting while the latter discloses a tight fitting mandrel for the inside diameter of a pipe.
Other prior art devices have also been disclosed for performing various operations on pipes. For example, in U.S. Pat. No. 2,749,803 (Anderson), an apparatus for trimming tube ends is disclosed. This apparatus includes a clamping means having two conical plugs located inside of the tube and a split ring wedge which is moved against the conical enlargement to clamp the apparatus to the tube. In U.S. Pat. No. 2,453,848 (Livingston et al), a facing tool for tubes is disclosed including expanding sections between wedging sections located inside of the tube. A cutter is manually rotated using a handle and a feeding wheel to appropriately face the pipe. A cutting tool for facing tubing to a desired length including a mandrel inserted within the tube is disclosed in U.S. Pat. No. 3,532,010 (Klintworth). A sloted tube holder is also disclosed in U.S. Pat. No. 1,336,466 (Lam).